ICAMS / Interdisciplinary Centre for Advanced Materials Simulation


Tight binding models from LCAO

Date: 29.09.2010
Place: ICAMS Scientific Retreat, Attendorn, Germany

Georg Madsen

Tight Binding (TB) methods can be seen as a parameterization of Linear Combination of Atomic Orbitals (LCAO) -methods, where the matrix elements of the Hamiltonian are parameterized and the rest of the DFT energy is approximated by terms dependent only on the atomic positions. In their modern formulation TB methods can treat charge transfer and spin-polarization, making them a robust compromise of accuracy and transferability versus computational cost and an attractive intermediate between DFT and empirical interatomic potentials. We will present a methodology for down-folding the LCAO Hamiltonian to a short ranged minimal basis. This has a practical advantage in making the construction of the TB model simpler and offers a more direct link between the TB and DFT energy functionals, thus facilitating future method development. We will highlight the differences between a flexible LCAO basis and the one used in an efficient TB-model. The methodology will be applied to calculate the trend in the TB basis when moving across the 3d series and it will be shown how it can be parameterized as two-center bond integrals.

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